The fabrication of large structures may involve the drilling of a large number of holes in the components of the structure. Conventional structures that require a large number of drilling operations include, for example, aircraft, missiles, ships, railcars, sheet metal buildings, and other similar structures. In particular, conventional aircraft fabrication processes typically involve the drilling of a large number of holes in wing sections of the aircraft to allow these sections to be attached to each other and to the airframe.
A variety of devices have been developed to facilitate drilling operations involving the drilling of a large number of holes. For example, U.S. Pat. No. 4,850,763 issued to Jack et al. discloses a drilling system that includes a pair of rails temporarily attached to an aircraft fuselage. A support carriage is slideably coupled to the rails and supports a drill assembly. A template attached to the aircraft fuselage provides an index for the desired locations of the holes that are to be formed in the aircraft fuselage. As the carriage is moved along the rails, a locking mechanism (or trigger) interacts with the template to securely position the carriage for a subsequent drilling operation.
Although desirable results have been achieved using the prior art drilling systems, some disadvantages have been noted. For example, the performance of prior art drill assemblies may be reduced when operating on relatively lighter, more flexible structures. In such cases, drill thrust may become too high and may cause undesirable bending or structural deflection of the workpiece, which may in turn result in reduced hole quality. Also, on such relatively light, flexible structures, the forces applied by the drilling system on the structure may require careful control to avoid overexertion against the structure. This may slow the manufacturing operation and reduce throughput. For the foregoing reasons, an unmet need exists for an improved support assembly for performing manufacturing operations, including drilling operations.